Method of and means for controlling alternating currents



Jan. 1925- r Y Y E. F. w. ALEXANDERSON METHOD OF AND MEANS FOR' CONTROLLING ALTERNATING CURRENTS' 1 Filed Nov. 20 1914 Inventor Witnesses V Hi Att 5516 Patented Jan. 6, 1925.

UNITED STATES PATENT OFFICE.

ERNST I. W. ALEXANDERSON, OF S CHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANSLA CORPORATION OF NEW YORK.

METHOD OF AND MEANS FOR CONTROLLING ALTERNATING CURRENTS.-

Application filed November 20, 1914. Serial No; 873,110.

1 0 all whom it may concern:

Be it known that L'EnNs'r F. W. ALEXAN- nERsoN, a citizen of'the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain ,new and useful Improvements in Methods of rent generator of comparatively large capacity may be varied between wide limits by variations in a controlling current of comparatively small magnitude.

A further object of my invention is to provide a transmitting system for wireless telephony wherein large amounts of energy may be controlled by the small current variations produced by sound waves in an 0rd1- nary telephone transmitter, in such a way that the sound waves may be faithfully reproduced in suitable receiving apparatus at a distant point. The utility of myunvention, however, is by no means limited to wireless telephony as it may equally well.

be employed in transmitting telephone currents through wires.

The novel features which I believe to be characteristic-of my invention are pointed out with particularity in the appended claims. The invention itself, however, with further objects and advantages will best be understood by reference to the following description taken in connection with the accompanying drawing, in which Fig. 1 is a simple diagrammatic representation of the apparatus and circuit connections wh ch may be employed incarrying my invention .into effect, and Figs. 2, 3, 4 and 5 show modifications thereof.

As indicated in Fig. 1 the source of high frequency alternating current 1 is inductively connected by means of the transformer 2 with the antenna 3. The amount of current flowing in the antenna is controlled by vary ing in a second circuit. a reactance comprising the two coils 4 and 5 wound around a magnetic core 6 is included in the antenna circuit. Wound upon the same core are two coils 7 and 8 through which the controlling current is caused to flow. The coils 7 and 8 are connected in opposition to each other, hence, the magnetizing action of the current flowing in coil 7 upon coil 5 is opposite in eifect to that of the current flowing/in coil .8 upon-coil 4.

As here indicated Furthermore, as c01ls 7 and 8 are connected in opposition the voltage induced in coil 7 by the h1gl1 frequency current is opposite to that induced in coil 8.' The respective coils are so designed that the voltage induced in coil 7 is equal to that in-.

duced in coil and therefore the effect of these voltages 1s neutralized. The combined inductance of coils 4 and 5 will vary as a function of the variations in the magnetization of the core 6, this change in inductance being due .to the varying magnetic reluctance at varying magnetic densities. Since the coils 7 and'8 are connected in opposition the combined inductance of coils 4 and 5 in the antenna circuit will be uniform for the two alternations of a complete cycle of the current. It will thus be evident that the current flowing in the antenna can be controlled by varying the amount of current supplied to the coils 7 and 8.

The greater theamount of energy which it is desired to radiate from the antenna the greater will be the variation required in the magnetizing force supplied to the coils 7 and 8 to give the desired control. If the controlling current applied to coils 7 and'8 is the current flowing .in an ordinary telephone transmitter, the amplitude of thecurrent flowing in the antenna may be varied in accordance with the variations in the amplitude of the telephone current. Inasmuch, however, as the energy variation whichmay be produced by an ordinary telephone transmitter is comparatively'small it is not possible to produce in this way sufficiently large variations in the magnetizing force .to control large enough amounts of energy to transmit sound waves over great distances. I have found, however, that by using suitable devices for amplifying the energy variations produced by the telephone transmitter and reproducing them in the controlling circuit it is possible to secure therein energy variations of sufiicient magnitude to control as large amounts of energy as are necessary to transmit sound waves over great distances. The magnetizing force supplied by the coils 7 and 8 ma be furnished by a. small current with a arge number of turns or bya larger current with fewer turns.- The reater the number of turns in the coil the greater will be the potential which it will be necessary to sup ply to the terminals. Hence, it will be seen that devices for amplifying the energy variation of the telephone current may be used which are adapted either for small currents and high potentials or for large currents and low potentials In the present case I have illustrated a simple form of apparatus of the first class, which is especially well adapted for the amplification of the energy variations in telephone currents because of the fact that the variations of the telephone current are reproduced without distortion. As here indicated the controlling current is derived from a direct current source of energy 9 which is preferably of high potential connected to the electrodes 10 and 11 of an electron discharge relay 12. The potential of the grid 13 in this relay is varied in accordance with the variations in the speech current flowing through the transmitter 14 by inductively connecting the transmitter circuit to the grid circuit by means of the transformer 15. The cathode 10 of the electron discharge relay 12 is provided with a battery 16 for heating it to incandescence. The envelope containing the electrodes 10 and 11 and the grid 13 is preferably exhausted to such a high degree of vacuum that with any voltage which may be applied to the relay the passage of cur: rent between the electrodes is not accompanied by appreciable gas ionization. It is well known that in a device of this type there will be a-flow of negative electricity from the cathode to the anode and that the amplitude of this current flow will vary in accordance with variations of potential of the grid interposed between the electrodes, hence, it will be apparent that with the organization indicated and described there will fiow through coils 7 and 8 a current which pulsates in accordance with the comparatively low frequency pulsationsof the current flowing in the transmitter. The magnetizing force applied to the core 6, however, may be made much greater than that which could be produced directly-by the telephone current. tude of the high frequency current flow in the antenna will vary as a function of the telephone current.

The current flowing in the control circui}g may be considered as a pulsatingpurren superimposed on a constant direct current.

The constant direct current will produce a As a result the ampli- V Meagan constant magnetization while the pulsating current will produce a magnetization proportional to the amplitude of the pulsations. Inasmuch as it will frequently be found desirable to adjust the degree of magnetization produced by the direct current component an adjustable rheostat 17 may be placed in the controlling circuit. In order, however, that the pulsating component of the current may flow through the circuit Without any unnecessary resistance this rheostat may be shunted by a condenser 18 which will allow the pulsating component to pass around the resistance.

his well known that if a source of alternating current of constant potential be supplied to an antenna and the frequency thereof be gradually increased the current in the antenna will increase to a maximum and then decrease. If the successive values of current be plotted, a peaked curve is obtained, the peak occurring when the frequency is that for which the antenna circuit is tuned and the slope thereof depending upon the electrical characteristics of the antenna circuit. If the natural period of the antenna circuit is varied by varying the inductance thereof it will be apparent that the current for a given frequency will be varied accordingly. In the normal operation of my device it will be found preferable to maintainv the normal value of the inductance of the antenna at such a value that the antenna does not have exactly the same natural period as the source of high frequency energy. It will also be found desirable to work entirely on one side of the peak of the curve mentioned. If the apparatus is adjusted to work on that side of the curve where the current is increasing, when the inductance of the antenna is increased, the natural period will be lessened and the current will tend to increase. On theother hand a decrease of inductance will increase the natural period and cause a decrease o i current. However, when working 0 the ascending part of the curve an increa e of inductance with an increase in the antenna current will cause an increase in the energy loss in the iron core of the inductance and'as a result the maximum value to which the antenna current will rise will be less than.under normal conditions; consequency there may be butlittle actual increase in the value of the antenna current.

If the apparatus is adjusted to work on the descending side of the curve, when the inductance of the antenna is increased, the natural eriod will become less and the current wil decrease. A decrease of inductance will increase the natural period'and cause an increase of current. Unless there is v available a source of energy, the frequency of which may be kept constant irrespective of the amount .of energy consumed, operation on this side of the curve will lead to extreme and irregular fluctuations in the frequency of the source of ener because of the fact that as the current ten s to decrease the natural period .of the antenna tends to decrease, causing a further decrease in the current, and'as a result the motor or other means employed to produce the energy Wlll tend to speed up.

In order to overcome these disadvantages which may arise in the operation of the system as shown in Fig. 1, the inductance instead of being placed in series with the antenna may be placed in shunt therewith as is indicated in Figs. 2 and 3. With the arrangement shown in these figures if the apparatus is adjusted to work on the ascending part of the tuning curve an increase in the controlling current will produce a decrease in the inductance of the coils 4 and 5. This will produce an increase in the current flowing through these coils with a consequent drop in the potential applied to the antenna. As a result the amplitude of the antenna current will fall below normal value as the natural period of the antenna increases. On the other hand if the controlling current is decreased the inductance of the two coils will increase and the antenna potential and current will increase. Since, however, the inductive losses are much less than when the controlling current is increasing the maximum amplitude ofi the current will become greater than under normal conditions. Hence, the variation in the antenna current, which maybe produced with a given variation of the, controlling current, will be much greater than when the coils are connected in series with the antenna. Thus it will be seen that by modifying the connection of the inductive device or by varying the adjustment thereof to work on either side of the tuning curve, it will be possible to produce various relations between the value of the controlling current and the antenna current. In any case, however, the antenna current will vary as a function of the variations in the'controllin-g current.

In Figs. 2 and-3, in addition toshowing the connection of the reactan'ce, in shunt to the secondary of the transformer 2, I have also illustrated organizations which are especially adapted for use in commercial stations in which a source of direct current of suflicient voltage to produce the controlling current in the organization shown in Fig. 1 is not available. While the reactance is shown in Figs. 2 and 3 as being connected in shunt to the secondary of transformer 2, it may equally well be connected to a tertiary circuit, as indicated in Fig. 4, in which a coil 34 is inductively related to the coils of transformer 2. It'may also be connected in shunt to the primary of transformer 2 and the alternator 1, as indicated in Fig. 5. As indicated in Fig. 2, the circuit of the magnetizing coils 7 and 8 includes an inductance 19 which may be loosely coupled to the tuning inductance 20 in the antenna. The current derived in this way is rectified by means of the mercury rectifier 21 and caused to flow through the transmitter 14 and coils 7 and 8. It will of course be understood that the transmitter 14 instead of bein connected directly in the circuit may be included in a separate circuit inductively related to the control circuit. The direct current source of energy 22 which is connected to the coils 7 and 8 through the inductance produces a constant magnetization of the core 6. This battery is connected in such a way as to oppose the electromotive force derived from the coil 19 and the rectifier 21. With this arrangement it will be seen that as the current flowing through the telephone increases the magnetlzation of the core 6 will decrease, thereby decreasing the current through the coils 4 and 5. 7 As a result the antenna current will increase and there will be a corre-' sponding increase in the rectified current which again reacts on the antenna circuit, etc. proportioned this reinforcing action may become so great that considerable amounts of energy may be controlledby the telephone current. Since the potential applied to the telephone varies as an inverse function of the resistance of the telephone a much greater current variation will be obtained than when a constant potential is applied to the telephone. This feature of my invention is described and claimed in my copending application Serial No. 715,723, filed "May 24, 1924, which is a division of the present application. In order that the impedance of that part of the antenna circuit including the coils 4 and 5 may be the minimum when the controlling current in the coils 7 and 8 is a maximum, it will be. found desirable to include in the-circuit an? adjustable condenser 24.

In Fig. 3 I have illustrated a similar organization with the exception that means is provided for amplifying the energy vari- If the Various elements are properly ations produced by the telephone transmitter. In this case the circuit which includes the magnetizing coils 7 and 8 and the recti fier 21 instead of being inductively related to the antenna is directly connected totwo points 25 and 26 in the antenna between which there is a suflicient difference of potential to produce the desired'current. It is well known that with a properly tuned antenna there exists between the earth and various points therein large differences of potential. In the present case the large difference of potential which exists between the earth and a selected point 27 in the antenna is applied to the'electron discharge relay f2 and the amount of energy which is thus diverted from the antenna is varied by varying the potential of the grid 13 by means of the transmitter 14 which is inductively connected to the grid13. The energy variations thus produced may be applied directly to the windings 7 and 8, although in most cases it will probably be found preferable toemploy additional windings 28 and 29 on the core 6, and supply to these additional windings these amplified energy variations. employed in this circuit for tuning it to the desired frequency. In this caseas in Fig. 2 the direct current source of energy 22 furnishes a constant source of magnetization. hen the magnetization of the core (5 is decreased because of the variation in the telephone current the antenna current is increased. This results in an increase in po-' tential between the points 25 and 26 and a corresponding decrease in the current supplied to the coils 7 and 8. Thus it will be seen that the same reinforcing action which is present in the arrangement of Fig. 2 takes place in this case. In the organization here illustrated the windings 7 and 8 may be designed to carry a comparatively large current with low potential while the windings 28 and 29 may be designed to carry a small current witha high potential. The constant component of the pulsating current flowing through the relay 12 may be so large as to saturate the core of transformer 31. If this is the case it may be desirable to provide an additional Winding 32 for the transformer supplied by a direct current source 33 in such a way as to neutralize the magnetization produced by the relay current.

In the description and in the claims which follow, when I speak of the antenna circuit as including :eactance coils, I wish it to be understood as meaning either the series or shunt connection inasmuch as the results whiclrmay be produced by either connection are similar. While I'have illustrated and described only three embodiments of my invention, I do not wish to be limitedto these specific applications, as it will be apparent that many modifications thereof may be made without departing from'the scope of the appended claims.

What I claim as new and desire to secure .by Letters Patent ofthe United States, is

1. The combination in a wireless signaling system of an antenna circuit supplied by a source of high frequency alternating current, a reactance included in said antenna circuit, a secondcir'cuit including a magnetizing winding inductively related to said reactance in such a manner that the impedance of the antenna circuit may be varied by varying the current flowing in said magnetizing winding, a third circuit having A variable condenser 30 maybe means therein for producing a variable current and means for amplifying and reproducing in the second circut the energy variations of the current in the third circuit, said amplifying means being capable of producing materially greater energy variatons than can be produced with an ordinary telephone transmitter. I

2. The combination in a wireless telephone system of an antenna circuit supplied by a source of high frequency alternating current, a second circuit associated therewith in such away that the impedance of the first circuit may be varied by varyingthe current flowing in the second circuit, a third circuit provided with means for causing a current flowing therein to vary in accordance with sound waves, and means for amplifying and reproducing in the second circuit the energyvariations of the current in the third circuit, said,- means being capable of producing in the second circuit energy variations materially greater than (an be produced by an ordinary telephone transmitter.

3. The combination in a wireless signaling system of an antenna circuit supplied by a source of high frequency alternating current, a reactance included in said antenna circuit, a second circuit including a magnetizing winding inductively related to said reactance in such a manner that the impedance of the antenna circuit may be varied by varying the current flowing in said-magnetizing winding, a third circuit having means therein for producing a current which Varies in accordance with sound waves, and means foramplifying and reproducing in the second circuit the energy variationsof the current in the third circuit, said means being capable of producing in the second circuit energy variations materially greater than can be produced by an ordinary telephone transmitter.

4. The combination witha circuit includ ing a rcactance and asource of high frequency alternating current of a second circuit including a magnetizing winding inductively related to said reactance in such a manner that the impedance of the first circuit will vary withvariations in the current flowing in saidmagnetizing winding, a third circuit having means for producing a variable electric current and means for amplifying and reproducing in the second circuit the energy variations of the third circuit, saidmeans being capable of producing in the second circuit energy variations materially greater than can be produced by an ordinary telephone transmitter.

5. The combination with a circuit including a reactance' and a source of high frequency alternating current of a second circuit including a magnetizing winding inductively related to said reactance in such a manner that the impedance of the first circuit will vary as a function of the variations in the current flowing-in said magnetizingcoils, a third circuit having means plied by a source of high frequency alternating'current, of a second-circuit associated therewithin such a way that the impedance of the first circuit will be varied in accordance with the variations in the energy supplied to the second circuit, a third circuit provided with means for causing a variable current to flow therein, means comprising an electron discharge relay for amplifying the energy variations of said variable current, and. reproducing the amplified energy variations in the second circuit, said relay being capable of controlling .a materially greater amount of energy than can be controlled by an ordinary telephone transmitter.

7. The combination in a wireless ,telephone system of an antenna circuit supplied by a source of high fr uency alternating current, a second circult associated therewith in such a way that the impedance of the first circuit will be varied in accordance with variations in the energy supplied to the second circuit, a third circuit provided with means for causing a current flowing therein to vary in accordance with sound waves. means comprising an electron discharge relay for amplifying the energy variations of said variable current, and reproducing the amplified energy variations in the second circuit, said relay being capable of controlling a materially greater amount of energy than can beicontrolled by an ordinary telephone transmitter.

8. The method of controlling the flow in an electric circuit of a high frequency alternating current which consists in producing in direct response to sound waves a pulsating current of small amplitude and small potential, amplifying the energy variations of said pulsating current, producing by means of said amplified energy variations a magnetizing field of varying strength and subjecting the high frequency alternating current flowing inlthe circuit .to the action of said magnetizil fg field in such a manner that the amplitude of the current will var as a function of the variations inthe pu sating current.

9. The combination in a wireless signaling system of an antenna circuit supplied by a source of high frequency alternating current, a reactance included in said antenna circuit, a second circuit includin a magnet-' izing'winding inductively relate to said reactance in such a manner that the impedance of the antenna circuit will vary as a function of the variations in theenergy supplied to said magnetizing winding, a third circuit provided withmeans for causing a pulsating current to flow therein, means comprising an-electron discharge relay for amplifying v the ener variations of said pulsating current an reproducing the amplified energy variations in the second circuit.

I 10. The combination in a wireless signaling system of an antenna circuit supplied by a source of high frequency alternating current,'a reactance included in said antenna circuit, a second circuit includin a magnetizing winding inductively relate to said reactance .in such a manner that the impedance of the antenna circuit will vary as a function of the variations in the energy supplied to said' magnetizing winding, a

third circuit having means therein for producing a current which pulsates in accordance with sound waves, means comprising an electron discharge relay for ampllfying the energy variations of said pulsating current and reproducing the amplified energy variations in the second circuit.

11. The combination in a wireless signaling system of an antenna circuit supplied by a source of high frequency alternating current, a reactance connected in shunt to said high frequency source, a second circuit including a magnetizing winding inductively related to said reactance in such a manner that the impedance of the antenna circuit may be varied by varying the current flowing in said magnetizing winding, and means for causing a pulsating current to flow in said second circuit.

' 12. The combination in a wireless signaling system of an antenna circuit supplied by a source of high frequency alternating current, a reactance connected in shunt in said antenna circuit, a second circuit including a magnetizing winding inductively related to said reactance in such a manner that the electromotive forces induced in the magnetizing winding by the action of the alternating current are neutralized and means for producing a pulsating current in said flow in said second. circuit which varies in accordance with sound waves.

14. The combination in a wireless telephone system of an antenna circuit supplied by a source of high frequency alternating .current, a reactance connected in shunt in said antenna circuit, a second circiiit including a magnetizing winding inductively related to said reactance in such a manner that the impedance of the antenna circuit may be varied by varying the current flowing in said magnetizing winding, and means for producing in said second circuit a current which varies in accordance with sound waves. I

15. The combination with a circuit supplied by a source of high frequency alternating current of a reactance connected in shunt to said current source, a second circuit including a magnetizing winding inductively related. to said reactance in such a manner that the current through said reactance will vary with variations in the current flowing in said magnetizing winding, and means for causing a variable current to flow through said magnetizing winding.

16. In a radio signaling system, a source of high frequency oscillating current, a radiating antenna system associated therewith, and a by-path circuit to earth for said antenna system including an audion and and means for controlling said audion.

17. In a radio signalin system, a source of high frequency oscil ating current, a' radiating antenna system associated therewith, and a by-path circuit to earth for said antenna system including an audion and signal actuated means for controlling said by-path.

18. In a radio signaling system, a source of high frequency oscillating current, a radiating antenna system associated therewith, and a by-path circuit to earth for said antenna system including an audion and voice actuated means for controlling the conductivity of the electric current through said audion.

19. In a radio signaling system, a source of high frequency oscillating current, a radiating antenna system associated therewith, and an evacuated vessel containing hot and cold electrodes forming a by-path to earth from said radiating antenna system and means for controlling said by-path. 20. In a radio signaling system, a source of high frequency oscillating current, a radiating antenna system associated therewith and an evacuated vessel containing wing, grid and filament electrodes, means for heating said filament electrode, a spur to the antenna connected to the wing electrode, an earth connection to the filament meager electrode and'a restistance varying device connecte' to the grid electrode.

21. In a'radio signaling system, a source of high frequency oscillating current, a radiating antenna system associated therewith, an evacuated vessel containing hot and cold electrodes, a spur to the,antenna connected to a coldelectrode of said evacuated vessel, and an earth connection to the hot electrode of said vessel and voice controlled means for varying the conductivity of the space between said electrodes.

22. The combination in a wireless signaling system of an antenna, a high fre naling system of a source of high frequency current, a radiating antenna system asso-' ciated therewith, and a shunt circuit in parallel to a portion of said antenna system, said shunt circuit including an electron discharge relay, and signal actuated means for controlling the current through said relay.

24. The combination in a wireless signaling system of a source of high frequency current,-a radiating antenna system associated therewith, and a shunt circuit in parallel to a portion ofsaid antenna system,

said shunt circuit including an electron discharge relay, and Voice actuated means for controlling the current, through said relay.

25. The combination in a wireless sig naling system of a source of high frequency current, a radiating antenna system associated therewith and an electron discharge relay comprising hot and cold electrodes connectedin a shunt circuit between points in said antenna system between which there is alarge difference of potentiaL'and means for controlling said shunt circuit.

26. The combination in a wireless sig' naling system of a source of high frequency current, a radiating antenna system associated therewith, an electron discharge relay comprising an incandescent cathode. cooperating anode and a conducting grid interposed between said cathode and anode, connections between said cathode and anode and points in the radiating antenna system between which there is a large difference of potential, whereby the device is included in a shunt circuit to a portion .of the 10- amplifying and reproducing the energy,

be receiver, and means for actuating said antenna system, and means for varying the quency continuous current, a signaling circuit supplied by said source, a modulating device -associated. with said source for modulating the current supplied to said signaling circuit, a source of signaling current, an electron discharge amplifier for variations of said source of signaling current, said amplifier being-capable of producing greater energy variations than can produced by 1 an ordinary telephone modulating device by the amplified energy variations of said 7 source of signaling current. I

28. Thefcombination in a high frequency signaling system of a source of high fre- I cuit supplied by said source; a secon quency', continuous current,-a signalin cir- 011.- cuit which includes a modulating device for modulating the current supplied to said signaling circuit, a third circuit provided with means for causing a variable signaling current to flow therein, and an electron discharge amplifier for amplifying and reproducing in the-second circuit ,the energy variations of the current in the third circuit, said amplifier being capable of pro-' ducing greater energy variations than can be pro receiver.

need by an ordinary telephone In witness whereof, I have hereunto set my hand this 18th day. of November, 1914.

ERNST W. ALEXANDERSON. v Witnesses:

BENJAMIN B. HULL, HELEN Onrono. 

